fix(sql): Fix QueryResult typings

closes #1893

plugins/sql/guest-js/index.ts

@@ -10,12 +10,12 @@ export interface QueryResult {
   /**
    * The last inserted `id`.
    *
-   * This value is always `0` when using the Postgres driver. If the
+   * This value is not set for Postgres databases. If the
    * last inserted id is required on Postgres, the `select` function
    * must be used, with a `RETURNING` clause
    * (`INSERT INTO todos (title) VALUES ($1) RETURNING id`).
    */
-  lastInsertId: number
+  lastInsertId?: number
 }
 
 /**